Air coupled seismic energy generator

ABSTRACT

An improved seicmic energy generator wherein pressurized air is supplied between a base plate and the earth&#39;&#39;s surface to form an air cushion therebetween, and the base plate is driven vertically upwardly and downwardly to generate and transmit a seismic force to the earth&#39;&#39;s surface via the air cushion.

United States Patent ['91 Miller [451 Apr. 17, 1973 [5 AIR COUPLEDSEISMIC ENERGY GENERATOR [75] Inventor: Dale E. Miller, Ponca City,Okla.

[73] Assignee: Continental Oil Company, Ponca City,Okla.

[22] Filed: Aug. 24, 1971 [21] Appl. No.: 174,343

[52] US. Cl ..l8l/0.5 VM, l8l/0.5 EC, 18110.5 H [Sl] Int. Cl. ..G0lv1/02 [58] Field of Search ..l8l/.5 VM, .5 EC,

[ 5 6 References Cited UNITED STATES PATENTS 3,547,218 l2/l970 Hamilton..l8l/.5 VM

OTHER PUBLICATIONS B. Geophysics Soft Touch" p. A-76, June 1970 r C. RNew Offshore Seismic Energy Source Creates lmplosion," Reprint fromWorld Oil, Sept. I967, Gulf Publishing Co.

Primary ExaminerBenjamin A. Borchelt Assistant Examiner-41. KinbergAnorneyloseph C. Kotarski et al.

[57] ABSTRACT An improved seicmic energy generator wherein pressurizedair is supplied between a base plate and the earth's surface to form anair cushion therebetween, and the base plate is driven verticallyupwardly and downwardly to generate and transmit a seismic force to'theearth's surface via the air cushion.

12 Claims, 3 Drawing Figures AIR COUPLED SEISMIC ENERGY GENERATORBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates generally to seismic energy generators and, more particularly,but not by way of limitation, to an improved seismic energy generatorfor coupling a force to an earth surface via an air cushion.

2. Brief Description of the Prior Art 7 In the past there have beenvarious devices constructed for producing a vibrational energyinput-into the earth, commonly referred to as vibrators, which wereutilized for seismic prospecting, the method and apparatus beingdescribed in the U.S. Pat. No. 2,668,128 issued to Doty et al. Somevibrators have been constructed for generating seismic waves within awater medium such a described in the U.S. Pat. No. 3,482,648, issued toG. L. Brown et al, for example; and there have also been vibratorsconstructed for utilization in a swampy or marshland type of area suchas described in the U.S. Pat. No. 3,365,019, issued to M. G. Bays, forexample (the Doty, the Brown, and the Bays patents each being assignedto the assignee or] the present invention). A seismic vibrator designhas recently been suggested wherein air was supplied to a plenum chamberof an air cushion vehicle through an air modulating apparatus, theplenum chamber and the air modulating apparatus being constructed 'to'create a modulated pressure wave which was applied to the earth surface.

SUMMARY OF THE INVENTION.

The present invention provides a seismic energy generating apparatus,having an air source for supplying pressurized air generally between abase plate and an earth surface, and a displacement apparatus fordriving the base plate in a vertical direction to generate and transmita force to the earth surface via the air cushion between the base plateand the earth surface.

An object of the invention is to provide a seismic generate, transmitand couple seismic forces to an earth surface 12, and generallyincludes: a base 14, having an upper side 16, a lower side 18 and anouter periphery 20; a skirt 22, which is connected about a portion ofthe lower side 18 of the base 14 to form with the base 14 and theunderlying earth surface 12 a plenum chamber 24; a displacement assembly26, having a portion connected to the base 14; and an air sourceassembly 28, which is connected to the apparatus 10 to supplypressurized air generally between the base 14 and the earth surface 12or, in other words, generally within the plenum chamber 24 to form anair cushion 30. In general, the base 14 is supported a distance 32 abovethe earth surface 12 via the air cushion 30, and is driven in agenerally vertical direction by the displacement assembly 26 in such amanner that the base 14 acts upon the air cushion 30 to generate a forcewhich is transmitted to the earth surface 12, the force being coupled tothe earth surface 12 via the air cushion 30. Although the apparatus 10is constructed to provide a seismic energy generating maximizetheverticql displacement thereof resulting from a particular force beingapplied thereto via the displacement assembly 26, during the operationof the apparatus 10. The air source assembly 28 includes an air source34 constructed to supply air at a predetermined pressure level and at apredetermined flow rate to form the required air cushion 30 forsupporting the base 14 above the earth surface 12 a distance 32. The

' air source 34 is connected to the base 14 via a pair of energygenerating apparatus particularly useful over a BRIEF DESCRIPTIONOFTI-IE DRAWINGS FIG. 1 is a side elevational view of a seismic energygenerating apparatus.

FIG. 2 is a bottom, plan view showing the base and the skirt of theapparatus of FIG. 1.

FIG. 3 is a perspective view showing the apparatus'of FIG. 1 supportedon an air cushion, support vehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings ingeneral, and to FIGS. 1 and 2 in particular, shown therein is a seismicenergy generating apparatus 10, which is constructed to flexible ducts36, each duct 36 being connected about an' air opening 38 formed throughthe base 14, the air source 34, more particularly, supplying pressurizedair between the base 14 and the earth surface 12 via the ducts 36 andthe air openings 38.

In one form, the pressure level and the flow rate of the air beingsupplied through each of the ducts 36 is separately controlled, and, inone other form, each of the ducts 36 is an extension of a main ductsupplied by' the common air source 34. The precise number of airopenings 38, interconnecting ducts 36 and the spacial disposition ofsuch on the base 14 may be varied for particular applications, thedetails of any particular design being determined to uniformlydistribute the pressurized air forming the air cushion 30.

The displacement assembly 26 includes a vibrator 40 connected to theupper side 16 of the base 14, a vibrator power supply 42, and aninterconnecting cable 44, the cable 44 being, more particularly, a hosetype connection in those instances wherein the vibrator 40 is of thehydraulic type. The vibrator 40 is drivingly connected to the base 14 toimpart vertical displacement thereto, in an acuated position thereof. Inone fon'n, the vibrator 40 and the vibrator power supply 42 areconstructed to impart a momentary, impact type of force to verticallydisplace the base 14 a predetermined distance, and, in one other form,to impart an oscillating type of force to vertically displace the base14 a predetermined distance at predetermined time intervals, forexample. The vibrator 40 may be any one of the known types of seismicenergy transducers, i.e. hydraulic, pneumatic, electro-mechanical,electromagnetic, mechanical, for example, the basic consideration beingthat the vibrator 40 imparts vertical movement to the base 14 in amanner controlled by the vibrator power supply 42 when actuated thereby.

In a preferred form, the skirt 22 extends a distance downwardly from thebase 14 toward the earth surface 12, and is constructed of a relativelyflexible material so that the skirt 22 is not destructively contacted byportions of the earth surface 12 during the operation of the apparatus10. The skirt 22 reduces the leakage of one form, the skirt 22 can beeliminated and the air source assembly 28 sized to provide a sufficientadditional flow of pressurized air to compensate for any increasedleakage of air.

During the operation of the seismic energy generating apparatus 10, thepressurized air is injected into the plenum chamber 24 from the airsource 34 at a sufficient pressure level and at a sufficient flow rateto form an air cushion 30 which supports the base 14 and the apparatusdisposed thereon a distance 32 above the earth surface 12, and tocompensate for the leakage of air generally through an air gap 46between the skirt 22 and the earth surface 12. The amount of seismicenergy generated by the apparatus 10 is related to the fractional changeof the volume of air and the resulting pressure level change of the airforming the air cushion 30 as the base 14 is displaced a given verticaldistance via the displacement assembly 26. It should also be noted that,as the distance 32 is increased or, in other words, as the thickness ofthe air cushion 30 is increased, a greater vertical displacement of thebase 14 will be required to generate a given pressure level change andtransmit a given seismic force to the earth surface 12. Also, since theseismic force to be applied to the earth surface 12 is related to theproduct of the pressure level change of the air cushion 30 and the areaof air cushion 30, the area of the air cushion 30 and consequently thearea of the base 14 must be increased proportionally to apply a greaterseismic force, assuming a constant pressure level change of the aircushion 30. The foregoing general relationships, along with other designconsiderations, such as cost, ease of construction, and mounting ofother equipment, generatlly determine the particular size, shape andmaterial of construction for the base 14. In a preferred form, however,the area of the portion of the base 14 forming the air cushion 30 issufficiently large to support the-static weight of the apparatus 10 witha given static pressure level of the air cushion 30.

In one form, the air source 34 and the vibrator power source 42 can besupported on the base 14, and, in one other form, the air source 34 andthe vibrator power source'42 are supported on a separate supportvehicle, which also provides the primary motive power for pulling andpositioning one or more of the apparatus 10. In this latter-mentionedform of the invention, the

design of the apparatus 10 does not have to be compromised to supportthe additional weight of the air source 34 and the vibrator power source42. One embodiment of such a support vehicle is diagrammatically shownin FIG. 3 and designated by the reference numeral 50.

The support vehicle 50 is of an air cushion type of vehicle, andincludes: a main air supply 52, which is typically an air compressor orblower, for supplying pressurized air within a plenum chamber (notshown) formed by a base 54 and surrounding skirt 56, the pressurized airwithin the plenum chamber supporting the support vehicle 50 generallyupon an air cushion. A pair of seismic energy generating apparatus 10aand 10b are supported on the support vehicle 50 via a boom assembly 58and 60, respectively, each boom assembly 58 and 60 being movablysupported on the support vehicle 50 and extending generally over oneside of the support vehicle 50. More particularly, each apparatus 10aand 10b is supported on the end of a cable 62 of one of the boomassemblies 58 and 60, the boom assemblies 58 and 60 being constructedfor moving and positioning each of the apparatus 10a and 10b atpredetermined positions generally over the earth surface. The apparatus10a and 10b are constructed substantially the same as the apparatus 10,described in detail above, the designations 10a and 10b being utilizedfor the purpose of clarity.

In this embodiment, the main air supply 52 also provides the pressurizedair for the air source 34a of the apparatus 10, the air supplies and thevibrator power source 42a is disposed and supported on the supportvehicle 50. Although the support vehicle 50 has been shown supportingtwo of the apparatus 10 (10a and 10b), in a particular application, moreor less of the apparatus 10 can be supported from a support vehicle, thetwo being shown for the purpose of description only. I

The seismic energy generating apparatus, described in detail before,thus, provides an economical and efficient means for producing seismicenergy and coupling such energy to the earth via an air cushion which isuseful over virtually any type of terrain, that is, soft earth surfaceor concrete or hard packed type of an earth surface. The seismic energyproduced via the apparatus can be of the impact type or of theoscillating type, depending upon the desirability in a particularapplicatron.

Changes may be made in the construction and the operation of the variouscomponents or the elements described herein without departing from thespirit and the scope of the invention as defined in the followingclaims.

What is claimed is: l'. A seismic energy generating apparatus fortransmitting a force to an earth surface, comprising:

base means; air source means supplying pressurized air generally'between the base means and the earth surface; and

displacement means connected to the base means for moving the base meansin a generally vertical direction to transmit a force to theearthsurface via the air between the base means and the earth surface.

2. The apparatus of claim 1 wherein the base means has an upper side, alower side and an outer preiphery; and wherein the apparatus in definedfurther to include:

a skirt means connected to the lower side of the base means andextending a distance downwardly therefrom, the skirt means encompassinga portion of the lower side of the base means and forming therewith aplenum chamber, the skirt means reducing the leakage of the pressurizedair.

3. The apparatus of cairn 2 wherein the skirt means is constructed of arelatively flexible material.

4. The apparatus of claim 1 wherein the base means is generally circularshaped.

5. The apparatus of claim 1 wherein the displacement means is definedfurther to include:

a vibrator connected to the base means for imparting verticaldisplacement thereto in an actuated position thereof; and

vibrator power source means connected to the vibrator to actuate thevibrator in one position thereof.

6. The apparatus of claim 1 wherein the displacement means imparts amomentary, impact type of force vertically displacing tee base means apredetermined distance.

7. The apparatus of claim 1 wherein the displacement means imparts anoscillating type of force vertically displacing the base means apredetermined distance at predetermined time intervals.

8. The apparatus of claim 1 wherein the air source means suppliespressurized air at a predetermined flow rate and at a predeterminedpressure level to provide an air cushion for supporting the base means apredetermined distance generally above the earth surface.

9. The apparatus of claim 1 wherein the base means includes an airopening means; and wherein the air source means is connected to the basemeans via a flexible duct means, the air source means supplyingpressurized air between the base means and the earth surface via theflexible duct means and the air opening means.

10. The apparatus of claim 1 defined further to include:

support means for supporting the base means in predetermined positions,comprising: support vehicle means having a portion thereof forming aplenum chamber;

main air supply means for supplying pressurized air generally within theplenum chamber of the support vehicle means; and

boom means connected to the support vehicle means and to the base meansfor moving and positioning the base means at predetermined positionsover the earth surface.

11. The apparatus of claim 10 wherein a portion of the displacementmeans and a portion of the air source means are each supported on thesupport vehicle means.

12. The apparatus of claim 1 wherein the displacement means and the airsource means are each supported on a portion of the base means.

l I. i i

1. A seismic energy generating apparatus for transmitting a force to anearth surface, comprising: base means; air source means supplyingpressurized air generally between the base means and the earth surface;and displacement means connected to the base means for moving the basemeans in a generally vertical direction to transmit a force to the earthsurface via the air between the base means and the earth surface.
 2. Theapparatus of claim 1 wherein the base means has an upper side, a lowerside and an outer periphery; and wherein the apparatus is definedfurther to include: a skirt means connected to the lower side of thebase means and extending a distance downwardly therefrom, the skirtmeans encompassing a portion of the lower side of the base means andforming therewith a plenum chamber, the skirt means reducing the leakageof the pressurized air.
 3. The apparatus of claim 2 wherein the skirtmeans is constructed of a relatively flexible material.
 4. The apparatusof claim 1 wherein the base means is generally circular shaped.
 5. Theapparatus of claim 1 wherein the displacement means is defined furtherto include: a vibrator connected to the base means for impartingvertical displacement thereto in an actuated position thereof; andvibrator power source means connected to the vibrator to actuate thevibrator in one position thereof.
 6. The apparatus of claim 1 whereinthe displacement means imparts a momentary, impact type of forcevertically displacing the base means a predetermined distance.
 7. Theapparatus of claim 1 wherein the displacement means imparts anoscillating type of force vertically displacing the base means apredetermined distance at predetermined time intervals.
 8. The apparatusof claim 1 wherein the air source means supplies pressurized air at apredetermined flow rate and at a predetermined pressure level to providean air cushion for supporting the base means a predetermined distancegenerally above the earth surface.
 9. The apparatus of claim 1 whereinthe base means includes an air opening means; and wherein the air sourcemeans is connected to the base means via a flexible duct means, the airsource means supplying pressurized air between the base means and theearth surface via the flexible duct means and the air opening means. 10.The apparatus of claim 1 defined further to include: support means forsupporting the base means in predeteRmined positions, comprising:support vehicle means having a portion thereof forming a plenum chamber;main air supply means for supplying pressurized air generally within theplenum chamber of the support vehicle means; and boom means connected tothe support vehicle means and to the base means for moving andpositioning the base means at predetermined positions over the earthsurface.
 11. The apparatus of claim 10 wherein a portion of thedisplacement means and a portion of the air source means are eachsupported on the support vehicle means.
 12. The apparatus of claim 1wherein the displacement means and the air source means are eachsupported on a portion of the base means.